Spain's Luis-Leon Sanchez won the 159km seventh stage of the Tour de France from Brioude to Aurillac.
The 24-year-old Caisse d'Epargne rider, 88th at the start of the day, broke clear with five kilometres to go.
A day of drama saw several retirements including that of former French champion Christophe Moreau.
Kim Kirchen of Team Columbia retains the leader's yellow jersey going into Saturday's stage, while David De la Fuente took the polka dot jersey.
Luxembourg's Kirchen is six seconds ahead of Australian Cadel Evans in the general classification.
"We defended the yellow jersey very well and I'll have it for another day tomorrow," said Kirchen. "I have a lot of confidence and this morning I had recuperated very well."
But it was a bad day for highly fancied Italian Damiano Cunego, who was involved in a crash 100 km from the finish that caused a split in the peloton. He lost 33 seconds to Kirchen, to drop to 17th in the overall general classification.
Sanchez was hugely aided by team-mate Oscar Pereiro, the 2006 champion after Floyd Landis was disqualified for doping, in the final stages and was able to celebrate metres from the finish, punching the air in delight as his pursuers failed to regain lost ground.
Germany's former race leader, Stefan Schumacher of the Gerolsteiner team, finished second and Italy's Filippo Pozzato came home third for Liquigas.
The stage included three sprints and five climbs, and produced a day of thrilling cycling at a high pace.
Britain's David Millar, of the Garmin team, attacked close to the summit of the category four climb at Villedieu after 52 km.
A four-man break formed, but because Millar began the stage in fifth place overall - just 47 secs behind Kirchen - he was never going to be given much rein, and his hopes of remaining clear of the peloton were further undermined by a puncture that eventually forced him to change bikes.
A combination of the high pace as the peloton pursued the group including Millar, the crash involving Cunego and strong winds split the field.
Josep Jufre, Vincenzi Nibali, Sanchez and De la Fuente comprised the day's most significant break. Jufre and Sanchez broke clear on the lower slopes of the Col d'Entremont with 65km left and were soon joined by the other two riders.
The four reached the summit of the category two Puy Mary one minute 30 seconds clear of the chasing pack, while De la Fuente moved to the top of the King of the Mountains classification after breaking clear on the final climb of the day.
The four riders were eventually caught but Sanchez then launched his decisive break to take the stage.
"I dedicate this victory to my brother, my parents, and to my team. We are a big family, a great team and I am sure that we can win the Tour," said Sanchez, whose brother died three years ago in a quadbike accident.
In addition to Moreau abandoning, Mauro Facci, Lilian Jegou and John Gadret also withdrew from the race. Jegou suffered a broken wrist after a particularly nasty crash in which he hit a tree.
Stage seven results:
1. Luis-Leon Sanchez (Spain / Caisse d'Epargne) 3 hrs 52 mins 53 seconds. 2. Stefan Schumacher (Germany / Gerolsteiner) +6 secs 3. Filippo Pozzato (Italy / Liquigas) same time 4. Kim Kirchen (Luxembourg / Columbia) same time 5. Alejandro Valverde (Spain / Caisse d'Epargne) same time 6. Oscar Pereiro (Spain / Caisse d'Epargne) same time 7. Samuel Sanchez (Spain / Euskaltel) same time 8. Josep Jufre Pou (Spain / Saunier Duval) same time 9. Christian Vandevelde (U.S. / Garmin - Chipotle) same time 10. Andy Schleck (Luxembourg / Team CSC) same time
50. David Millar (Britain/Garmin-Chipotle) +33 secs 145. Mark Cavendish (Britain/Team Columbia) +21.53.
Overall standings (after seven stages):
1. Kim Kirchen (Luxembourg / Columbia) 28 hrs 23 mins 40 secs 2. Cadel Evans (Australia / Silence - Lotto) +6 secs 3. Stefan Schumacher (Germany / Gerolsteiner) +16 4. Christian Vandevelde (U.S. / Garmin - Chipotle) +44 5. Denis Menchov (Russia / Rabobank) +1:03. 6. Alejandro Valverde (Spain / Caisse d'Epargne) +1:12. 7. David Millar (Britain / Garmin - Chipotle) +1:14. 8. Stijn Devolder (Belgium / Quick-Step) +1:21. 9. Oscar Pereiro (Spain / Caisse d'Epargne) same time 10. Thomas Lovkvist (Sweden / Columbia) Same time
148. Mark Cavendish (Britain/Team Columbia) +45.15.
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